Most airports, especially large airports, currently simultaneously handle large numbers of arriving and departing aircraft of different sizes and body types. The successful management of a large volume of aircraft ground traffic requires careful control of all aircraft ground movement, particularly the movement of departing aircraft. Aircraft parked at a gate or docking area in an airport prior to departure are typically positioned with the nose of the aircraft facing the gate or docking structure, which may or may not be attached to the airport terminal. Upon departure, the aircraft must move in reverse and make one or more turns before reaching a taxiway prior to taxi and takeoff. Arriving aircraft are moving in a forward direction and turning as required to travel from the runway to a gate or docking structure as the departing aircraft are leaving. Departing aircraft must be maneuvered carefully in a reverse direction to avoid not only incoming aircraft traveling toward the gates, but also baggage carriers, tugs, and other airport ground vehicles on the trip between the gate and the taxiway. Reverse ground movement of an aircraft may also be required to move the aircraft into or out of a hangar or to a location for maintenance.
An aircraft can be moved in reverse from a parked position by starting the aircraft's main engines and reversing them to drive the aircraft in a reverse direction. This process, known as reverse thrust, is problematic and can be dangerous. An aircraft engine operating in reverse thrust pulls foreign object debris from the aircraft's environment into the engine and throws it forward, usually in the direction of the gate or airport terminal. The potential for injury to ground personnel, ground vehicles, and airport structures from foreign object debris (FOD) and from ground jet blast can be significant. In addition to the turbulence and noise created by an aircraft's engines in operation, moreover, the adverse impact on air quality and fuel costs must also be considered. It has been estimated that about 3200 pounds of fuel is used in an hour by an idling aircraft engine. An aircraft's engines idling between push back and takeoff, even if only about 20 minutes a day, can increase fuel costs by millions of dollars. The use of reverse thrust is prohibited at many airports, moreover. Dependence on the use of a departing aircraft's main engines is neither a safe nor a reliable push back procedure.
At the present, aircraft leaving a gate, docking structure, or simply a parked position near an airport terminal are typically assisted in their travel in a reverse direction by a special tow vehicle or tug that temporarily connects to the aircraft in the area of the forward nose wheel. Once attached to the aircraft, the tug pushes the aircraft in the reverse direction required to clear the gate to a location where the aircraft main engines can be turned on to move the aircraft in a forward direction. The tug is then detached from the aircraft and moved away, and the aircraft is ready to taxi to a runway for takeoff.
The movement of tugs and tow vehicles generally contributes to ground vehicle traffic. Tugs, in addition, must be monitored to keep track of their locations so they may be moved to the next location by the time a tug is needed to push back a departing aircraft. Many aircraft departure delays are the direct result of tug unavailability. Although pilot controlled and remotely controlled tugs are disclosed in the art, for example in U.S. Pat. No. 6,928,363 to Sankrithi and U.S. Pat. No. 6,305,484 to Leblanc, respectively, such tugs are not widely available, and a ground crew team is still required to monitor and move tugs and to carry out the push back process.
The ground crew must also ensure that no part of an aircraft structure will impact any fixed object or other aircraft or vehicle. The size of the ground crew assigned to push back functions depends on the size of the aircraft and usually includes at least three people: one to drive the tug or pushback vehicle, one to walk in the vicinity of one of the aircraft wing tips, and one to direct the push back maneuver and handle communications with the responsible aircraft cockpit crew member. Depending on the type of external tow vehicle or tug used for push back, additional ground personnel can be required to inactivate the aircraft steering, attach and remove the tow vehicle, and then reactivate the aircraft steering while communicating these actions to the flight crew. Ground crew must also return the tugs or tow vehicles from the location where they are detached from the aircraft to the gate area for reuse with another aircraft.
A variety of tow vehicles or tugs is known in the art, and all require careful operation to ensure safe push back of an aircraft. The aircraft push back process may use, for example, the type of widely known heavy tow vehicle that is attached to the nose wheel of an aircraft by a tow bar employing one or more kinds of pins to disable the aircraft nose wheel steering during pushback and/or to prevent the aircraft from being mishandled by the tug. A “towbarless” type of tug, such as that described in U.S. Pat. No. 5,480,271 to Franken et al, may also be used to achieve push back. Whichever type of tug is used, ground personnel are required to perform specific tasks to achieve safe and effective push back, including, among other tasks, inserting and removing pins, communicating the status of the pins to the cockpit crew, and ensuring that damage to the landing gear and injuries to the ground crew does not occur during tug engagement or push back. Each type of tug presents specific disadvantages. Specialized tow bars are typically required to tow different aircraft, and an airport must have a selection of specific types of tow bars ready to meet the needs of different aircraft. If the proper tow bar is not available, an aircraft cannot be connected to a tug and must wait for the correct tow bar, delaying push back and aircraft departure. Additionally, tug tractors are usually powered by gas or diesel engines, which negatively impacts airport ground noise and air quality with their emissions and increases airport facility fuel costs. Tugs without tow bars are often powered by electricity and offer improvements in maneuverability and control, but many require some type of adapter to enable the tug to move a particular type of aircraft. A similar size ground crew is needed for the operation of a tug with or without a tow bar, however, and tug movement and availability must still be monitored. Moreover, an airport operator is still required to maintain a fleet of tugs or tow vehicles and operators to push back departing aircraft and to otherwise move aircraft on the ground. With the cost of a single tug in excess of a quarter of a million dollars, this represents a substantial investment for an airport.
A further consideration raised by the present state of airport and aircraft pushback operations relates to the ground congestion found in most large airports. Multiple airlines conduct both push back and landing operations for multiple aircraft virtually simultaneously. This strains not only the available towing equipment, but also the available ground personnel. Aircraft turnaround times can be adversely affected when tow bars, adapters, tugs, or ground crews are not available when needed. Neither the airline nor the flight crew has any control over this situation. Moreover, if an aircraft is damaged during push back or causes damage to another aircraft during push back in a congested airport, and the damage is not detected prior to takeoff because ground crew were busy elsewhere, aircraft safety could be compromised.
The prior art, therefore, fails to provide a powered self push back method and system integral to an aircraft that can be controlled and operated by the aircraft pilot in cooperative communication with a minimal ground crew to effectively accomplish safe push back of the aircraft from a gate or docking structure independently without the use of external tow or tug vehicles or the aircraft main engines.